Analog-digital converter



Juy 17, 1962 R. w. TRIPP ETAL ANALOG-DIGITAL CONVERTER 19 Sheets-Sheet 1Filed March l2, 1958 ATTORNEY.

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ATTORNEY.

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ATTORNEY.

July 17, 1962 R. w. TRIPP ETAL.

ANALOG-DIGITAL CONVERTER 19 Sheets-Sheet 5 Filed March l2, 1958ATTORNEY.

July 17, 1962 R. w. TRIPP ETAL 3,045,230

ANALOG-DIGITAL CONVERTER Filed March l2, 1958 19 Sheets-Sheet 6 July 17,1962 R w, TRIPP ETAL 3,45,230

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ROBERT W. TRIPP a JAMES l .W|NGET.

ATTORNEY.

July 17, 1962 R. w. TRIPP ETAL v 3,0455230 ANALOG-DIGITAL CONVERTERFiled March 12, 1958 19 Sheets-Sheet 8 To Fleau 48) 1-conm=noL Y To 4oo-PANEL (OVERRIDE SIGNAL) ROBERT W. TRIPP JAMES L. WI NGET. BY

ATTORNEY.

July 17, 1962 R. w. TRIPP ETAI. 3,045,230

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ATTORNEY.

19 Sheets-Sheet 10 Filed March 12, 1958 -IHI'- INVENTORSJ ROBERT W.TRIPP 8x JAMES L..W|NGET. BY

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July 17, 1962 R. w. TRIPP ETAL.- 3,045,230

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July 17, 1962 R. W. TRIPP ETAL..

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INVENTORS.' ROBERT W. TRIPPB; JAMES L. WINGET.

ATTORNEY.

July 17, 1962 Filed March l2, 1958 R. W. TRIPP l ET'AL ANALOG-DIGITALCONVERTER 19 Sheets-Sheet 13 @.Yl *fw swITcI-I AMPLIFIER FoR INDucTosYNCOMPUTER ouTPuT ign/5 +I44 v. MULTIPLE INPUT I FEEDBACK AMPLIFIER 5 (20oKc) OUTPUT WVM INVENTORS: ROBERT W. TRIPP 8I BY JAMES L. WINGETATTORNEY.

July 17,- 1962 R. w. TRIPP ETAL. 3,045,230

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ATTORNEY.

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ATTORNEY.

R TRIPP 'E1-AL. 3,045,230

ANALOG- DIGITAECONVERTER 19I Sheets-Sheet 16 SHIFT REGISTER PANEL TOFIG.2I b

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ATTORNEY.

7 UNIT 2 July 17, 1962 R. w. TRIPP ETL 3,045,230

ANALOG-DIGITAL CONVERTER Filed March l2, 1958 19 Sheets-Sheet 18 July17, 1962 R. w. TRIPP ETAL 3,045,230

ANALOG-DIGITAL CONVERTER Filed March l2, 1958 19 Sheets-Sheet 19 POwERSUPPLY CONTROL @.34

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AT TORNEYI Unite States Patent O 3,045,230 ANALOG-DIGHAL CONVERTERRobert W. Tripp, Bronxville, and James L. Winget, Harrlson, N.Y.,assignors to Inductosyn Corporation, Carson City, Nev., a corporation ofNevada Filed Mar. 12, 1958, Ser. No. 720,949 7 Claims. (Cl. 340-347) Theinvention relates to an analog-digital converter for converting a shaftrotation into electrical digital form.

it is frequently necessary to convert a shaft angle into some form ofdigital number that is suitable for a particular computer. While theseresults can be obtained by photographing the scales of an accuratelydivided circle, together with some form of time reference, and latermanually converting this information to digital form and storing it onpunched cards or the like, this is a long laborious process and subjectto operator errors.

An object of the invention is to obtain the angles, in digital form,directly from the shaft rotation. The angle data can be recorded,together with the necessary time reference, on film, magnetic tape, orany other convenient and suitable medium.

Theoretically, a shaft rotation can be divided into digital form by theuse of a set of suitable commutators. That is, one commutator would have2 segments, the next 4, the next 8 and the next 16 and so on-When thedigital information is to be transformed into binary form. Obviouslythis method is limited by the number of segments that it is practical toplace within a reasonable space on a commutator. This problem can be atleast partially solved by incorporating `gearing mechanisms to operatesome of the commutator segments at speeds that are some power of 2higher than those of the input shaft with the corresponding smallernumber of segments required. Again, this method is limited by thepractical accuracies that can be obtained with gears. This accuracy willdepend upon the space available and the life that is `expected of theequipment (gear wear). However, for most reasonablesize equipment,accuracies of about one minute can be expected.

The problem of a high accuracy analog-digital converter could be solved,through the development of an accurate gear step-up of high ratio suchas about 64 to 1. This would make it possible to build a system, usingcommutators, to an overall accuracy of a few seconds. The inventionmakes this possible by the use of Inductosyn 1 as data-transmissioncomponents. Basically, the Inductosyn is an inductive device with manyof the characteristics of an ordinary twoaphase synchro or resolvertwoimportant differences being that the Inductosyn has a very high accuracyand is a multiple-pole device. The lnductosyn is a l-speed device(direct-shaft driven) but the voltages and synchronous points of thesystem are similar to those that would be observed in an ordinarytwo-phase resolver system using a gear ratio such as 64:1.

In lnductosyn in the system may be compared to a highly accurateresolver (one minute of arc) geared up 64 times without any gearingerror. The Inductosyn is mounted directly on the input shaft. TheInductosyn consists of two flat, round, glass disks having printedconductor patterns. One disk, the rotor, contains one pattern only,corresponding to the single secondary winding of the 40G-cycle resolverdescribed later, and employed in the coarse portion of the preferredform of the invention. The other disk contains two patterns in spacequadrature, corresponding to the primary winding of the resolver. TheInductosyn type of position measuring transformer is described andclaimed in Patent 2,799,835 dated July 16, 1947 which discloses bothlinear and rotary forms. The rotary form is used in the presentinvention for the trans- 1 Trademark.

, 3,045,230 Patented July 17, 1962 mission and repetition of angularposition data. The windings on the disks have one pole per conductor andan air core, the secondary voltage varying in magnitude according to therelative angular position of the disks over a cycle measured by anangular spacing center-tocenter of three adjacent radial conductors onthe rotor disk. The Inductosyn is similar in action to a resolver, buthaving a larger number of poles. For example, the Inductosyn may have128 poles or 64 pole cycles per 360 of the Inductosyn rotor.

Since the inherent accuracy of the Inductosyn is a few seconds of arc atany point within 360 degrees of rotation, and the accuracy of theresolver can be a few minutes of arc, a gear ratio that is sucientlyaccurate for the analog-digital converter is obtained.

The system described up to this point would seem to meet therequirements of an analog-digital converter of high accuracy. There isone serious drawback however. Suppose that it is desired to work to anaccuracy of five seconds of arc. This means that the circle would bedivided 2 18 or 262,144 parts. (There are 1,296,000 seconds in acircle). By limiting the number of segments on a commutator to 64 therequired gear ratio between the lspeed input shaft and the last set ofcommutators would be 4096. This means that with the input shaft rotatingat l rpm., the highest speed commutator sections would rotate at 4096rpm. This limits the possible speed of the input shaft. Otherwise thissystem should be quite practical.

The invention makes it possible to obtain this digital information atsomewhat higher speeds. For this purpose, the seven highest-speedcommutators would be eliminated and the required information is obtainedfrom another Inductosyn, mounted directly on the l-speed shaft. This isdone as follows:

An Inductosyn on the input shaft is used as a receiver. The transmitteris a set of voltages obtained from a binary counter replacing the sevendigits dropped off by the above seven commutator segments. This set ofvoltages is applied to the two stator windings of the Inductosyn. Theerror voltage from the Inductosyn operates a gate allowing the counterto advance the voltages on the Inductosyn in the same manner as would bedone by manually rotating an Inductosyn transmitter. The counter wouldcontinue counting (forward or backward as the case may be) until theerror voltages reach null. `In this way, the correct count would be setup for the present angle of the Inductosyn and the remaining elevencommutator segments. The principles of the circuitry and generalarrangement are shown in FIG. 1 for such a system, that would be capableof operating up to about 10 ripm. of the input shaft. This correspondsto about 40,000 counts per second.

In the preferred form of the invention shown in FIGS. 2 to 24, thecoarse portion of the system employs a resolver as an error measuringmeans of the coarse system and a l-speed (direct shaft driven)Inductosyn having 64 synchronous points is employed as the errormeasuring means of the ne system. Both the coarse resolver and the ineInductosyn operate on the same principle as the fine portion of the formof invention in FIG. l, as follows: Advantage is taken of the fact thatif two voltages whose amplitude ratio is proportional to the tangent ofan angle 0, are impressed across the two members of the primary winding,the voltage across the secondary winding will be a sine function of theposition of the input shaft with which the secondary winding rotates.This is explained as follows: Assuming that a voltage sin 0 is appliedto one input winding and a voltage cos 0 to the second input winding,the amplitude ratio is sin /cos 0, or tan 0.

